Do satellite observations of atmospheric temperatures agree with surface-based observations and model predictions?

July 2, 2007

Yes. Atmospheric temperatures have been measured by a series of satellites dating back to 1979. Because each satellite operated differently, scientists have disagreed about how to correct the data for instrument errors and how to merge all the satellite data into a long-term record.

Over the past decade, different “merging” techniques resulted in different long-term temperature trends, not all of which showed the warming that climate models predicted should have occurred. Some early analyses even suggested that parts of the troposphere (lower atmosphere), where warming was expected, had cooled. The lack of an unequivocal warming trend in the troposphere was sometimes used to challenge both the reality of human-induced global warming as well as the reliability of climate models.

To help resolve the discrepancies, the U.S. Climate Change Science Program undertook a comprehensive review of surface and atmospheric temperature observations and trends. The group identified and corrected errors in early versions of satellite and weather-balloon data, and concluded “For recent decades, all current atmospheric data sets now show global average warming that is similar to the surface warming.”

Early versions of atmospheric temperature data sets from satellites suggested that the lower atmosphere had warmed little if at all since 1978 (blue line). Newer versions (green and orange lines) show a warming trend that is similar to the warming measured at the Earth's surface. Blue line is Version D data from University of Alabama in Huntsville (UAH), developed in 1999. Green line is UAH Version 5.3, developed in 2010. Orange line is Remote Sensing Systems (RSS) version 3.2, developed in 2008. (Graph by Robert Simmon, based on UAH data from the National Space Science and Technology Center, and RSS data from Remote Sensing Systems, sponsored by the NOAA Climate and Global Change Program.)

Some uncertainties remain, however, particularly in the tropics. While all the long-term atmospheric data sets now show a warming trend, they do not all show the amplified warming (greater warming of the atmosphere than the surface) that models predict. According to the U.S. Climate Change Science Program report, this remaining uncertainty may be due to additional errors in the observational data sets (the explanation favored by the report authors) or to limitations in the models’ ability to simulate the impact of global warming on different atmospheric layers.